Author：AXYZdong Automation Engineering Male
Two key attributes of files ： file name and route （ Indicates the location of the file on the computer ）
Windows On , The path is written with a backslash \ As a separator between folders
OS X and Linux On , Use forward slashes / As the separator of the path .
Current working directory
Every program running on the computer , There is one. “ Current working directory ”, or cwd. There is no file name or path starting from the root folder , Are assumed to be in the current working directory .os.getcwd() Function to get the string of the current working path , You can use os.chdir() Change it .
>>>os.getcwd() # Get the current working path ,cwd(current work directory)： Current working path 'D:\\Python Study'
Absolute path and relative path
use os.makedirs() Create a new folder
>>>import os
>>>os.makedirs('.\\read1')
>>>os.makedirs('D:\\Python study\\read2')os.makedirs('.\\read1')： Relative paths , Means to create... Under the current working directory read1 Folder .
os.makedirs('D:\\Python study\\read2')： Absolute path , stay D Discoid Python Study Create under folder read2 Folder .
To ensure that the full pathname exists , If the intermediate folder does not exist ,os.makedirs() All necessary intermediate folders will be created .
os.path modular
os.path The module contains many useful functions related to file names and file paths .os.path yes os Module in module ,import os You can import it .os.path Complete documentation of the module ：http://docs.python.org/3/library/os.path.html .
Deal with absolute （absolute） Path and relative （relative） route
os.path.abspath(path) Returns the string of the absolute path of the parameter , Facilitate the conversion of relative path to absolute path .os.path.isabs(path) Determine whether the parameter is an absolute path , If so, return True, Otherwise return to False.os.path.relpath(path,start) Will return from start To path The string of the relative path of , If not provided start , Default the current working directory as the starting path .os.path.dirname(path) Will return a string , contain path Everything before the last slash in the parameter .（ The directory name is returned ）os.path.basename(path) Will return a string , contain path Everything after the last slash in the parameter .（ The basic name is returned ）os.path.split(path) Return the directory name and basic name of a path at the same time , Get the tuple containing these two strings .>>>import os
>>>path = 'C:\\Windows\\System32\\calc.exe'
>>>os.path.abspath(path)
'C:\\Windows\\System32\\calc.exe'
>>>os.path.isabs(path)
True
>>>os.path.relpath(path,'C:\\Windows')
'System32\\calc.exe'
>>>os.path.dirname(path)
'C:\\Windows\\System32'
>>>os.path.basename(path)
'calc.exe'
>>>os.path.split(path)
('C:\\Windows\\System32', 'calc.exe')View file size and folder contents
os.path.getsize(path) return path Folder size under path .os.listdir(path) return path List of file name strings under path .>>>path = os.getcwd() >>>os.path.getsize(path) 4096 >>>os.listdir(path) ['.idea', 'Data Visualization', 'demo', 'demo.py', 'demo_1.py', 'paper.png', 'PDF synthesis ', 'text.py', 'turtle', 'watermark', 'wordcloud', '__pycache__', ' lantern .py', ' Crawling pictures .py', ' veil .jpg']
Check the validity of the path
>>>path = os.getcwd()
>>>os.path.exists(path)
True
>>>os.path.exists('D:\\read')
False
>>>os.path.exists('D:\\Python study')
True
>>>os.path.isfile(path)
False
>>>os.path.isdir(path)
True
>>>os.path.isfile('D:\\Python Study\\demo.py')
Trueutilize os.path.exists() function Can be determined DVD Or whether the flash drive is currently connected to the computer . （ I don't have... On my current computer F Discoid ）
>>>os.path.exists('F:\\')
False Plain text file ： Contains only basic text characters , Does not contain fonts 、 Size and color information . Such as ： with .txt Extension text file , with .py Extended name Python Script files .
Three steps for reading and writing files ：
open Several modes of opening files Character Meaning --------- --------------------------------------------------------------- 'r' open for reading (default) 'w' open for writing, truncating the file first 'x' create a new file and open it for writing 'a' open for writing, appending to the end of the file if it exists 'b' binary mode 't' text mode (default) '+' open a disk file for updating (reading and writing) 'U' universal newline mode (deprecated)
Create in current directory one.txt text file , And successively write Hello world！ and my name is axyzdong.
>>>onefile = open('one.txt','w') # Open text in write mode
>>>onefile.write('Hello world!\n')
13
>>>onefile.close()
>>>onefile = open('one.txt','a') # Open text in add mode
>>>onefile.write('my name is axyzdong')
19
>>>onefile.close()
>>>onefile = open('one.txt')
>>>content = onefile.read()
>>>onefile.close()
>>>print(content)
Hello world!
my name is axyzdongUse shelve The module will Python The variables in the program are saved to binary shelf In file .
step ：
shelve.open() Open files can be read and written by default , Like a dictionary shelf Value has keys() and values() Method , return shelf Keys and key values in .
Use occasion ： Suppose there is a dictionary , Save in a variable , You want to save this variable and its contents , It can be used at this time pprint.pformat() Function to hold this variable , And write it in .py file . This file will become a module , You can call it when you need it .
>>>import pprint
>>>characters = {'one':'a','two':'b'}
>>>pprint.pformat(characters)
"{'one': 'a', 'two': 'b'}"
>>>file = open('characters.py','w')
>>>file.write('characters = '+ pprint.pformat(characters) + '\n')
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>>>file.close()
>>>import characters
>>>characters.characters
{'one': 'a', 'two': 'b'}
>>>characters.characters['one']
'a' such , There will be a in the current working directory characters.py file , It only contains One line of code characters = {'one': 'a', 'two': 'b'}
Create a .py The advantage of the file is ,.py A file is a text file , Anyone can use a simple text editor to read and modify the contents of the file .
reference
1：Python Programming fast : Automate tedious work / ( beautiful ) Svegart (A1 Sweigart) Writing ; Translated by Wang Haipeng . Beijing : People's post and Telecommunications Press ,2016.7
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